Process of reducing formic acid.



No. 867,575. PATENTED 00T. a, 1907.

7 c. ELLIS a; K. P. MOELROY.

PROCESS 0F RBDUGING PORMIG ACID.

'AEPLIVOAIION FILED MAY 2, 19.07.

hereinafter set forth and as claimed.'` x

" UNITED STATES PATENT-formen.

o ArtLE'roN ELLIS, .oF WHITE rLAINs,- NEWY0EK, AND KAEL P. MCELROY, or WASHINGTON, DIsTRIoToFooLUMBIA. y,

PROCESS 0E REDUCING Font/iro non).

No.'s67,575.*

. speciication'ofLetters.Patenti- Patented oet. s, 1907.

Application sled nay 2, 1907: sra1N0.,371",'3a7.

To all whom it may concern:

vBe it known that we, CARLE'roN ELLrs and KAELy P. McELRoY, citizens of the United States, residing, respectively, in White Plains, county of Westchester, and State of New York, and in Washington, District of Columbia, have invented certain new 'and usefull Improvements in Processes of Reducing Formic Acid; and-We hereby declare the following to be a full, clear, and exact description of the same. f This invention relates to processes of reducingformic acid and consists in a method of electrolytically reducing formic'acid to produce methyl alcohol, formaldehyde and condensation products; all as more fully In ordinary electrolysis of monobasic fatty acids and their salts the negativel radical or ion, in this case RiCOO- (in which R indicates a fatty radical) goes to the anode while the hydrogen or other positive ion goes to the cathode. The group R000-, however, being incapable of separate existence breaks up at the anode in the absence of any other group with whichl it can unite, generally giving carbon dioxid and a hy drocarbon, or', sometimes, giving oxidation products:`

- with co-evolved oxygen. Formicacid and its salts 'usually yield carbon dioxid and Water. There is no The formation of negativeions in a solution is strictly proportional to the concentration of the H ions therein,I4

no more being produced than are equivalent to' s uch H ions. Formic acid and the higher lfatty acids are relatively little capable of dissociating" in solution with formation of negative`and H ions. In the presence ofav strong, freely dissociating mineral acid, the concert-'- trationof H ions from this latter source reaches-a maximum and' such less dissociative, weaker-fatty acids tend to remain associated. In other words, .the group RCOOHl tends to remain as such withoutv formation of .peculiar property known as overvoltage,'" such as H and R.COO-ions; without'formingnegative ions which cantravelto the anode and decompose there.

. In a two'compartment,eleotrolytic celLthevatty acid may be retained inthe cathode ico'mpartmentwithout traveling tothe anode to any extent, and in the cathode."

y, compartment it may be readily reduced with formation 7 of usefulproducta geousas preventing oxidation and waste off-the fatty acid. f

itssolutions is, so to speak, purely secondary; a reduction by the H ions formed at the cathode. Two main reductions arepossible: a replacement of the saturating Oxygen of the carboxyl by hydrogen With formation of methyl alcohol, orareplacement'of the hydroxyl by hydrogen, forming formaldehyde. Apparently both reactions ordinarily occur and both products are formed, their relative proportions depending, at least to some extent, upon the temperature, the relative concentration of the electrolyzed acids, the current density, the voltage and other conditions. It is possible that the formation of the methyl alcohol, at least to'some extent, vis due to a secondary reaction, the further reduction of the formaldehyde by excess of hydrogen. Long treatment with large excess of electro lytic hydrogen sometimes produces methane, but this is, of course, to be avoided. Other conditions being equal, low current density appears to form formaldehyde preferentially while high current density gives a greater'proportion of methyl alcohol. Both products are ordinarily formed and both are valuable.

Formic acid being somewhat sensitive to the dehydrating action of 'strong concentrated acids, with production of carbon monoxid and Water, it is better to work at'rather low temperatures and in the presence of vmineral acidnot too concentrated.-` In the presence of rather strong" sulfuric acid,polymerized formaldehyde is likely to be produced to some extent. Any freely dissociating mineral acid is suitable, but sulfuric acid is at present'zpreferred, as it ionizes more freely than phosphoric and does not attack anodes like hydrof chloric. A- ten per centfsolution of sulfuric acid.. is amply strong, reducing the amount of negative formic ions to a negligible concentration. It isfrequently advantageous to have `the strength of the sulfuric acid in the neighborhood often percent. i

A s facilitating the reaction, cathodes possessing the lead cathodes, are advantageous.. Spongy nickel, iron ',or4 cobalt cathodesarealso advantageous because of the lpeculiar relation of'these metals to hydrogenating reactions, such asthis. vPlatinized platinum may also be employed.' Preferably the 'current is kept rather low. The presence offacilitating catalytics, such as ycerium salts, isadvantageous. In the electrolysis there'isordinarily no special advantage, in the specific employedin the-'form of one 'of its salts, such as calcium or sodium formate, a proper excess of mineral acid being used, but in continuous operations it is ordinarily better to use the formic acid itself.

Any ordinary electrolytic cell maybe used, but, as stated, it is considered better to use a two-compartment device, the compartments being separated by the.

ordinary porous wall and the formic acid kept around the cathode. .q

, In continuousr operation, an advantageous method of does mayreadily be recovered for return to the electrolyzer in the subsequent fractionation of the alcoholic distillate,`where an acid-free distillate is desired. For many purposes however the amount of formic acid in the first distillate is not enough to be injurious and it may even be desirable, formic acid having good disinecting powers and, since it is a fairly strong acid, enhancing the solvent powers of the alcohol for some pur'- poses. The distillation part of the cycle may be performed in any ordinary column still suited to handle acid liquids. Another method of distillation which offers the advantage of not requiring-expensive apparatus, is to pass the liquid from the cathode compartment in thin films or layers over suitable surfaces and there strip it of low boiling constituents by a current of gas, also preferably traveling in a closed cycle through a suitable condensing apparatus.

- The distillate or condensate ordinarily forms a solution of methyl alcohol, formaldehyde and some formic acid, and can readily be handled for fractionation and recover-y of pure strong products in the usual fractionating apparatus, such as column stills. It may, however, as stated, be employed direct for any purpose for which it is suitable.

In the described method ofoperation, the same quantity of mineral acid, e. g., sulfuric, ma .if course be employed for a long time. With the formic acid should be added enough water to replace that taken out in the stripping operation, and liquid from the anode compartment may be occasionally added to the cathode compartment to keep the concentration of the mineral acid within the desired limits.

In the accompanying illustration is shown onecom? bination of apparatus of the many types adapted to perl form the described process.

, In this showing, 1 designates, as a whole, an ordinary two-compartment electrolytic cell divided byporous partition 2. It contains the anode 3, which may be of carbon, platinumor any other suitable conductor, and the cathode, 4, both being connected to a suitable source of current, 5. The double-valved funnel 6 allows introduction of formic acid, sulfuric acid or water. Thermometer 7 permits observation of ternperature and the heating or cooling jacket 8, provided with inlet and outlet 9 and` l0, allows control of the same. Valved pipe Il is provided for withdrawal of liquid from the anode chamber. Outlet pipe 12 perseams mits Withdrawal of liquid from the cathode c/hamber by means of pump I3 and delivery by means of distributing device 14 into a stripping chamber l5. This chamber, as shown, contains a steam coil lG, preferably of lead pipe, and may also contain, as shown, coke or other material, 1.7, of large surface. From the chamber the liquid which has trickled down the steam coil und coke is returned to the cathode chamber by means of pipe 18, provided with a valved outlet lf), for use when it is desired to empty the cathode chamber or test the liquid by analysis.

Leading from the top of the stripping chamber or Coke tower, is a pipe 20, provided with fun 2l and passing through a cooling and condensing jacket 22 into a seal-pot 23. The seal-pot has a valvcd outlet 24 for withdrawing a portion of its contents from time to tim o. The uncondensed gas mass from thc stripping chamber bubbles through the liquid in the seal-pot and returns through pipe 25 into the stripping chan'iber., lhis pipe is preferably given, as shown, an upward .sl-.mt and ends somewhat above the bottom of the stripping chamber.

The Stripping tower shown muy be replaced by un ordinary column still if desired, but thc arrangement shown is simple and effective. y

When insoluble salts are formed in the cathode chamber, as in the use of formates of the alkaline earths with sulfuric acid, they may be readily 'removed by funnel bottom 27, valved at 28. This also serves to remove any solid polymerized formaldehyde which may form.

The operation of: this apparatus is obvious, lhe formic acid is introduced Continuously, or from time to time, through the valved funnel into the cathode bath. As it is reduced thereinby the action of the current, the acid containing the reduction products is withdrawn `and' stripped of the same in the stripping chamber by the action of the circulating gas mass, which may be air or any suitable gas. Using air, its oxygen is usually withdrawn by oxidation of the methyl alcohol, etc., leaving a residue of inert nitrogen. The closed circuit for the gas has the advantage that no methyl alcohol or formaldehyde is lost by escaping condensation in the condensing means. When stripped of volatile bodies, the cathode liquid is returned to the cathode chamber to serve anew.

In discontinuous operation, the cathode compartment may be emptied from time to time through the funnel bottom shown. This structure is also advantageous in handling calcium formate and similar formates forming insolublesulfates by double decomposition with sulfuric acid. For instance, a mixture of a solution of calcium formate with the correct amount of sulfuric acid may be directly introduced through the funnel. As sulfate of calcium accumulates, it is Withdrawn by the hopper bottom. Y j

Other fatty acids of the monobasc fatty acid series, such as acetic, prOpiOniC, butyric and the' like may be similarly treated by this method and with this apparatus, giving reduction products valuable as solvents and for other purposes.

What We claim is:

1. The process of reducing acids of the rnonohasc fatty acid series with formation of aldehydes and alcohols which consists in electrolyzng the same in the presence o1' a stronger mineral acid.

l 2. 'The process of reducing acids of the monobasic fatty series with the formation of aldeixydes and alcohols which consists in electrolyzing the same in the presence of sulY furie acid.

The process of reducing formic acid which consists in electrolyzing the samein the presence of a stronger mineral acid. y

4. The process of reducingformic .acid which Iconsists in electrolyzing the same in the presence of sulfuric acid.

5. The process of reducing formic acid which consists in electrolyzing the same in a cathode compartment in the presence of a stronger mineral acid.

G. '.lhe process-of reducing formic acid which consistsv in elcctrolyzingl the same in a cathode compartment in the presence of `sulfuric acid.

7. 'lheprocess of reducing fatty acids` which consists in` electrolyzing 'the same in the presence of a stronger mineral acid, removing a portion of the hath from time to time, distilling out reduction products and returning the residual liquid to serve anew.

8. '.lhe process of reducing formic-acid which consists -in clectrolyzini.r `the same in the presence of a stronger mineral acid, removing a portion of the bath from time to time, distilling out reduction products and returningthe residual liquid to serve anew.

i). The process of reducing fatty acids which consists in elecrrolyzing the same in the presence of a stronger mineral acid, removing a portion of the reduced liquid, passing the same throughs stripping still and returning to the electrolytic bath with addition of more fatty acid.

10. vThe process of reducing formic acid which consists in electrolyzing the same in the presence of a stronger mineral acid, removing a portion of the reducedlliquid, passngthe same through a stripping still and returning to the eleetrolytic bath with addition of more formic acid.

11. In the eiectiolytic reduction of organic compounds, the process of continuously recovering volatile reduction products which consists in removing a portion of the electrolyzed and reduced liquid, passing the same through a stripping still to remove such volatile reduction prod ucts, and returning the stripped liquid to the clectrolytic hath.

1'2. In the electrolytic reduction of organic compounds, the process of continuously recovering volatile reduction products which consists in removing a portion of the -electrolyzed and reduced liquid, passing the same through a stripping still in iilmiform condition against a circulating. gas mass to remove such volatile products, and returning the stripped uquio to the eiectmly'nc bath.

13. 1n the clectrolytic reduction of organic compounds,

'the process ofcontinuously recovering volatile reduction.

products which consists in removing a portion of the electrolyzcd and reduced liquid, heating and filming the same, circulating a gas mass in closed circuit through a condenser, `over the filmed liquid and back to the condenser and thereby stripping said liquid of volatile products, and returning the stripped liquid for renewed electrolysis.

14. In the electrolytic reduction of organic compounds, the process of recovering volatile reduction products -which consists in filming and heating the electrolytically zrcduced liquid and while in such filmed and heated con- 

